Manchester City will spend in the transfer window to find a "quality" replacement for striker Sergio Aguero and to improve the squad, chairman Khaldoon Al Mubarak has revealed. Argentina international Aguero, City's all-time topscorer with 260 goals, played his last game in the Champions League final defeat to Chelsea and has <a href="https://www.thenationalnews.com/sport/football/pleasure-and-pride-to-play-with-messi-sergio-aguero-unveiled-as-barcelona-player-in-pictures-1.1233134">joined Barcelona on a two-year deal</a> after a decade-long spell at Etihad Stadium. "We lose a very important legend in <a href="https://www.thenationalnews.com/sport/football/2021/10/31/sergio-aguero-what-happened-to-barcelona-striker-and-why-was-he-taken-to-hospital/" target="_blank">Sergio Aguero</a>," Al Mubarak told mancity.com. "They are very hard shoes to fill, but I'm confident that we will find the right player to fill those shoes. "There are other areas within the group, within the team that obviously need investment. Not too many. It's not about numbers, it's about quality. “I think the squad is a phenomenal squad. You don't win the Premier League and you don't reach the Champions League final if you don't have an incredible squad, and we have that. "One of the things I've learned over the years is you need to constantly bring in talent into the team, refresh and particularly when you are at a high level and when you're on the top." City won their third league title in four years this season, finishing 12 points ahead of rivals Manchester United. Al Mubarak said City, who also won the League Cup, will not stand still despite their domestic success. "Having won the league, it is not the time to sit back and be content. That would be your biggest mistake," he said. "This is the time to send a strong message, that there's no contentment, that you're not satisfied with just winning the league. “That's great, but you want to win it again and you are committed and you are bringing more talent that is going to compete, not for the squad, but for the starting XI." On the disappointment in Porto, he added: "I feel very proud of what this team has accomplished. "When you reach a Champions League final – the pinnacle in football, the pinnacle of sports – I think it is an incredible achievement, a remarkable season by any description. "But it is also a culmination of years of hard work to reach a level of consistency, a level of expectation that this club has reached now – which is a club that will compete year in, year out. "You can't win every year but year in, year out we are going to be there. It is about going forward and, whenever we have setbacks, regrouping and coming back stronger. "As sad as we all are at losing the Champions League final, we will be back in that final and more importantly [with] these titles we will always be there, that I promise." Al Mubarak also discussed the positive relationship he enjoys with manager Pep Guardiola, who has now won eight trophies in the five years since his arrival and signed a new two-year contract in November. “This partnership has been a great partnership,” he said. “He’s in the right environment, he's got the right infrastructure around him. We have the greatest trust and the greatest relationship, and we've achieved so much. “So, I think the journey goes on and it will go on as long as Pep is happy and we are happy. “To the Man City fans, I tell you, just be positive, be confident, enjoy these moments, look forward to the next season and we'll take it one season at a time.”